Apparatus for controlling the supply of abrasive to grinding machines



June 8 1926.

H. K. HITCHCOCK APPARATUS FOR CONTROLLING THE SUPPLY OF ABRASIVE TO GRINDING MACHINES Filed May 12 1925 FIELI.

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#vvsMa June 8 1926 H. K. HITCHCOCK APPARATUS FOR CONTROLLING THE SUPPLY OF ABRASIVE TOAGRINDING MACHINES FIGS- W 5 m m A E M W. E H

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.C IlZL Jane 8, 1926. 7 1,587,526

H. K. HITCHCOCK APPARATUS FOR CONTROLLING THE SUPPLY OF ABRASIVE TO GRINDING ,MACHINES Filed May 12 1925 4 Sheets-Sheet 5 FIGLE.

Jane 8, 1926. 1,587,526

H. K. HITCHCOCK APPARATUS FOR CONTROLLING THE SUPPLY OF ABRASIVE TO GRINDING MACHINES Filed May 12, 1925 4 Sheets-Sheet 4 FIE.7.

//V MENTOR Patented June 3, 126..

HALBERT E. EITCHC OCK, 'OF PITTSBURGH, PEHNSYLVIA.

APPARATUS FOR CONTROLLING THE SUPPLY ABRASIVJE TO GRINDING MACHINES.

.. Application filed May 12, 1925.

The invention relatesto apparatus for the grading and applying of abrasive, such as sand, to grinding apparatus, and involves a modification of the apparatus disclosed in my application Serial No. 687,702 for performing a similar function. The invention has for its principal object the provision of improved means for regulating the sand feeding apparatus by the density in the grading tank, so that such density is maintained substantially constant and so that the degree of fineness of the'sand lying at different levels is maintained substantially constant. (ertain (embodiments of the invention are illustrated in the accompanying drawings wherein: i a

Figure 1 is a eneral arrangement on a small scale showing the entire apparatus. Fig. 2 is a side elevation of the regulating device in position in a grading tank. Fig. 3 is a plan view of the apparatus of Fig. 1, and in addition shows in a diagrammatic way the electrical connections and apparatus for controlling the feed of sand from the sand hopper. Fig. 4 is an elevation of the upper end of the balancing tubes viewed from the back; F ig. 5 is a side elevation of the construction of Fig. 4. Fig. 6 is a diagrammatic view illustrating a modified ar rangement of contacts and electrical connections for application to the construction of the apparatus of Figs. 1 to 5. AndFig. 7 is another diagrammatic view similar to that of Fig. 6, but illustrating another modificatlon.

Referring to the general arrangement as illustrated in Fig. 1, the referencenumeral 1 indicates a conical grading tank designed to feed a mixture of sand and water from "different levels therein to a. grinding machine, which is not shown. As is common in this art, the sand and water from the grinding machine is returned to a sump 2 beneath the tank, from which it is pumped up into the tank by means of a pump 3 operated by a suitable motor, not shown. Fresh sand is supplied to the sump 2' from the hopper 4, which swings back and forth about the shaft 6 and controls the supply of sand which is fed into the trough 7. This trough discharges into the rotating screen 8 located 1n the upper portion of the sump 2. A connecting rod 9 operated froma crank disc 10 serves to open and close the valve, the crank disc being has at its lower end a valve 5 which Serial No. 29,718.

driven from a suitable motor 11. Mounted loosely on the shaft 6 carrying the valve 5 is an arm 12 to which is rigidly secured the magnet winding 13 and this arm 12 is engaged and rocked by the connecting rod 9. The core of the magnet winding 13 is adapted to contact with the arm 14 which is mounted upon the shaft 6 so as to swing the valve. /Vhen the winding of the magnet 13 is energized, the arms 12 and 14 are magnetically connected so that the swinging of the arm 12 by the rod 9 opens and closes the valve 5, thus permitting a timed discharge of sand which is carried'to the sump 2.

When the current through the magnet 13 is cut off or reduced beyond a certain point, the connection between the arms 12 and 14 is released so that the arm 12 may be swung by the connecting rod 9 without actuating the valve 5 so that the .feed of sand is discontinued. Thus by completing and disc0n-' tinuing the flow of current through the winding of the magnet 13, the sand feed is controlled. This making and breaking of the circuit through the magnet is controlled from the grading tank 1 by means of a hydrometer therein. Up to this point, the construction as described is the same as that set forth in Fig. 4 of my pending application heretofore referred to, and the present invention relates principally to the form of hydrometer employed and the means for controlling the valve 5 from this hydrometer.

In the controlling hydrometer of the present application, a pair of tubes 15 and 16 are employed instead of the single tube of my application referred to, such tubes being of different length and extending to different levels a and b in the tank. These tubes have enlargements 17 and 18 at their upper ends, which enlargements lie partly above the level of the tank and partly below such level. Secured to the sides of these enlargements arc pairs of'knife edges 19 and 20 by means of which the tubes are suspended upon a beam 21 balanced upon a knife edge 22 carried by the bracket23, such bracket being suitably supported upon a platform 24 carried by the topof the tank, as illustrated. The beam 21 is provided with a slide barv25 at one side and upon this is mounted the balancing weight 26. The beam 21 also carries on its rear side the arm 27 provided at its lower end with a set screw 28 (Fig. 4) adapted to operate the push button switch 29. This push button switch is of the type used upon doors, being spring held in closed position when the arm 27 occupies the position shown' 16 induced by variations in the density of the mixture in the tank between the levels a and Z).

With theparts. in the position illustrated in Fig. 4, with the switch closed, a circuit is established from the main lines 30 and 31 via the connection 32, the relay magnet winding 33 and the connection 34, thus causing the relay arm 35 to moveto the left against the tension otthe spring 36' and complete the connection between the contacts 37 and 38. This completes the circuit from the main 30 to the main 31 via the connection 39, magnet winding 13, connection 40 and the relay arm 35 connecting'the contacts 37 and 88 so that at this time the winding 13 is energized, thus connecting the arms 12 and 14, and the reciprocation of the connecting rod under these conditions opens and shuts the valve 5, thus providing a feed of sand to the sump 2. At this time, the lamp 41 is also lighted, since it is in parallel with the connections 39 and 40. This condition continues as long as the density of the mixture in the tank does not rise above a predetermined point. \Vhen it does rise above a predetermined point 'and the level of the liquid in the long tube 15 is raised relative to thatof the tube 16, the tube 15 moves down relative to the tube 16, thus swinging the arm 27 (Fig. 4) to the left and opening the switch 29. This breaks the circuit through the relay winding 33 and the arm 35 is moved to the right by the spring 36 so that it breaks the connection between the contacts 37 and 38 and the cir-' cuit through. the magnet 13 and the light 41 is interrupted. As a result,,the arm 12 is disconnected from the arm 14 so that there is no longer any reciprocation of the valve and the feed of sand is thus stopped and the light 41 is cut out. The movement of the relay arm 35 to the right makes a connection between the contacts 42 and 43, thus completing the circuit'through the lamp 44, so that this lamp lights, thus indicating that the density of the mixture has risen above the point foiywhich the apparatus is setand also that the sand feeder is not working. This condition obtains until the withdrawal ot the mixture from the tank 1 reduces its density to a point where the tubes 15 and 16 resume their former position. thus making contact at the switch 29 and again starting the feed of the valve 5-bv reason of the energizing of the winding 13 as heretofore explained, the lamp 41 being again lighted and the lamp 414 extinguished.

As pointed out in my application heretofore referred to, the level of the liquid in the hydrometer tubes 15 and 16 rises above the level of that in the tank, since the tubes contain clear water which is less dense than the mixture surrounding the lower ends of the tubes. Any abrasive entering the lower ends of the tubes tends to settle out,'so that the density of the liquid is less in the tubes than outside of them and the height of the liquid supported correspondingly greater. The level in the long tube 15 will be higher than that in the tube 16 since the pressure in the tank at the lower end of thetube 15 is greater than the tank pressure at the lower end of the tube 16 and the difference in the level is thus controlled by the weight of the column of the mixture in the tank lying between the levels a and b.

This arrangement involving the two hydrometer tubes, instead of a single one, such as that of my application heretofore referred to, presents certain advantages as compared with the single tube. "With the single tube, the tendency toward vertical movement is governed by the weight ofthe column of mixture (outside the tube) extending from the bottom of the tube to the surface of the mixture, while with the two tubes the tendency toward relative movement is governed by the weight of the column of mixture lying between the levels a and b. The latter is the more desirable condition, since the new sand is being fed in adjacent the space between the levels a and Z), so that' the regulation of the supply is immediate, the device responding quickly to variations in density in the differential column. Again, it is most important to maintain the density of the mixture of coarse abrasive and water constant, and it is in this portion of the mixture that the differential column is located.

In order to make the apparatus respond more quickly, the pipes 45 and 46 are located so as to discharge small streams of water downward into the upper ends of the tubes 15 and 16. This counteracts the tendency of the inflow at the bottom of the tank to carry fine sand up into the tubes, so that the lower portions of the tubes are kept free from sand. As pointed out before. the device depends for its operation on the relative density of the mixture ins de and outside the tubes, so that the keeping of the tubesfree from sand, which would add to the density therein, makes for a more positive operation.

Fig. 6 illustrates a somewhat different arrangement of contacts operated by the arm 27 and a different operation of theindicat ing lights. There are two push button switches 47 and d8 instead of the single and 61, so that both memes switch of the Fig. 1 construction and the actuation of these switches by the relative movement of the tubes 15 and 16 causes a showing at the red lamps a9 and green lamps 50 to indicate working conditions somewhat more fully than is the case with the arrangement of Fig. 1. hen the'parts are 'in-the 58, the connections 54 and 58 being the main teed lines of the system to which current is supplied from a suitable source. At the same time, current is'also supplied through the green lamps 50 via the connections 59, 60 sets of lamps show color, which condition is designed to indicate normal density in the mixture of the tank with the sand feeding mechanism operating.

It now the. mixture becomes too thin, the short tube 16 moves down so that the arm 27 moves to the right and opens the switch 48. This breaks the circuit through the green lamps 50 so that they no longer show" color. The operator is thus advised that his mixture is too thin and, if this condition continues, some adjustment must be made to increase the thickness of the mixture such as speeding up the motor which operates the valve arm 12 (Fig. 3) or by shifting the connection between the connecting arm 9 and the arm 12, so as to give a wider opening of the valve 5 at each reciprocation of the rod 9.

If the mixture in the tank becomestoo thick, the long tube moves down and the short one moves up, thus swinging the arm 54 to the left and opening the switch 47. This breaks the circuit through the wires 52 and 53 so that the valve 5 is no longer operated, and also through the red lamps 49 so that only the green lamps 50 show. It the red light continues to show for a considerable period withoutany re-lighting ot the lamps 50, the operator is advised that the valve 5 must be stuck open, possibly by a stick or a stone and that this condition must be looked after. If the valve 5 were not stuck open, the red lights would show in a short time after cutting oii the feed through the valve 5, since without this feed, the withdrawal of the-mixturefrom the tank would so reduce its density that the tube 16 wouldmove up relatively to the tubes 15, movin the arm' 54 to the position illustrated in ig. 6, at which time. the switch 4.7 is o ened.

Fig. 4 illustrates another modification for controlling the fioiv of current from the main {eed lines 62 and 63 to the inagnet 13 (Fig. In this construction, three sets of colored lamps are employed, the lamps 66 being preferably green, the lamp 67 and the lamps 68 being yellow. The arrangement is such that when the apparatus is working normally and the feed valve 5 is being operated by its motor, the green lamps 66 and yellow lamps 68 are lighted. If the motor for the valve 5 should stop, or the valve 5 should stick in closed position, or the sand should become exhausted from the sand hopper, the green lamps only wll be lighted. When the mixture in the tank be comes too dense and the flow of current to the magnet winding 13 is cut otl, the green lights 66- are extinguished and the yellow lamps 68 lighted so that at this time, the yellow lights only show. Should the mixture become still more dense, incident to the valve 5 being stuck open, so that the feed of sand continues regardless of the stoppage of operation of the motor operating the valve 5, thered lamp 67 will become lighted in addition to the yellow ones, thus indicating the abnormal condition specified which calls for immediate attention upon the part of the operator.

" Tn this particular construction of Fig, 7, the tubes 15 and 16 operate pressure rheostats instead of push button switches as in the other forms off-construction heretofore described. There are two of these pressure rheostats 69 and 70 arranged above the lever 71 upon which the tubes 15 and 16 are suspended and which is pivoted upon the knife edge 72. The lever 71 is connected with the two rheostats by means of the rods 73 and 74 so arranged that when the lever 71 hasforce applied to it tending to rotate it in a clockwise direction, the discs in the rheostat 69 are tightened, while those in the rheostat 70 are loosened, and when force is applied to the lever 71 in the reverse or counterclockwise direction, the discs in the rheostat 69 are loosened and those in the rheostat 70 are tightened. The apparatus includes three relay coils or windings 75, 76 and 77 arranged to operate the relay arms 78, 80 and 79, normally held open by means of the springs 81, 83 and 82 respectively. The manner in which this is accomplished will be best understood by reference. to the diagram in Fig. 7, in which R is a resistance sufficiently large to require one half of the voltage from the circuit 62 and 63 when the current is flowing normally. Beyond the resistance It, the current flowing through the circuit 84 divides, part of it going through the connection 89, coil 75, connecbeing red 0) through the connections 64 and 65.

tion 88, coil 76 and connections 87 and 97.

The other part of the current passes through the resistance 69 and 70, and connections 86 and 97. The coil 7 7 is connected between the coils 7! and 76 to the connection 85 between the rheostats 69 and in series. W hen the density in the zone 06-?) is exactly right, the pressure on the two rheostats 69 and 70 should be equal and no current will flow through the coil 77, and the same current will be flowing through the coils and 76. Atthis time, the tension springs 81 and 83 are so adjusted that the magnets and coils 76 and 76 will cause the contacts 78 and to be closed, thus lighting the lamps 66 and 68 and energizing the magnet (corresponding to 13, Fig. 8) on the valve of the sand hopper through the connections 6tand 65 so as to start the sand feed. The sand feed is preferably adjusted to be great- -er than that required to maintain the required density in the zone ab, so that the density at this point gradually increases, thus forcing the water up through the tube 15 and increasing the pressure in the rhco stat 69 and decreasing the pressure in the rheostat 70, which reduces the resistance of rheostat 69 and increases the resistance of rheostat 70, thus causing part of the current that heretofore has passed through coil 75 to travel around through the rheostat 69 up through the connection 96, through the coil 77 back to connection 88 through the coil 76, connection 87 and 97 to the main circuit, thus weakening the pull of the'magnet 75, increasin the 76 and starting die pull of the magnet 77. In this condition, the lamps 68 are lighted and the lamps 66 are extinguished. Should,

' for any reason, the sand not stop flowing from the sand hopper-because of a leakage of the valve or the valve being held open by some obstruction, the sand continues to go into the system, the water is forced higher up into the tube 15, the pressure on the rheostat 69 is increased, thereby lowering its resistance, while the pressure on the rheostat 70 is decreased, thereby increasing its resistance. This causes more current to pass through the rheostat 69 up through thereonnection 96, through the coil 77 until such a.

time as the pull of the coil 77 will over come the resistance of the spring 82, causing the contact 79 to close, thus completing the circuit through connection 99, and lighting the lamp 67 which denotes that something is wrong with the apparatus that requires inimediate attention Should the valve close properly when the contact 78 is broken, thus stopping the sand from going into the sump, the density in the zone 0-6 will be gradually reduced, thereby relieving the weight until the pressure in the rheostats will be e which case the current flowing tirough the magnet 75 will close the contact 78, thereby lighting the lamp 66 and energizing the magnet at the valve at the sand hopper. Should the sand be exhausted from the hopper, or should it not fiow freely enough pull of the magnet,

means for the feed means ing the feed ualized, in

memes to maintain the density in the zone a b, the weight in the tube 15 will gradually decrease, thereby increasing the pressure on the rheostat 70 and decreasing the pressure on the rheostat 69, which would result in the increase in resistance in rheostat 69, and a decrease in the resistance in rhcostat 70, thus causing part of the current that has been flowing through the magnet 76 to pass down through the connection 86, magnet 70, connection 96, coil 77 back to the circuit 88, thus weakening the pull on the contact arm 80 and allowing the spring to break the contact at y, thus extinguishing the lamps 68. Should the supply of sand to the sump continue to be insufiicient to maintain the density in the zone ab, the column of water in the tube 15 would still farther fall, the pressure in rheostat 70 would be increased still farther, and the pressure in rhcostnt 69 decreased, causing more current to be diverted from coil 76 up to coil 77. This would cause the contact 79 to be pulled down by the magnet 77 lighting the lamp 67 showing that the system was not functioning normally and calling attention to the fact that more sand must be provided. Inasmuch as it requires more current in the coils 75 and 76 to pull the contact arms down to make contact than it does to hold them there p'hen the apparatus is actually properly a(l JuSted and in actual operation, there will be times when the apparatus is functioning properly and the lights 66 and 68 are not both burning, but in the arrangement just. described, there should be always one set of these lights burning, so that, if for any cause the supply of current to this system is shut oil, the operators attention is immediately called to this fact.

What I claim is:

1. In combination in apparatus for rcgir lating the density of a mixture of abrasive and water in a tank, a feeding device for supplying sand to the tank, and regulating comprising a pair of upright tubes in the tank extending down to difi'erent levels therein and having enlargements at their upper ends extending above the surface of the mixture in the tank, a lever upon which the tubes are supported so that they tend to counterbalance each other, and means actuated by the relative vertical movement of the tubes for governmeans.

2. In combination in apparatus for regulating the density of a mixture of abrasive and water in a tank, a feeding device for supplying sand to the tank, and regulating means for the feed means comprising a pair of upright tubes in the tank extending down to ditl'erent levels therein and having enlargements at their upper ends extending above the surface of the mixture in the tank, a lever upon which the tubes are supported so that they tend to counterbalance each other, and an electro-magnetic means actuated by the relative vertical movement by tubes for governing the feed means.

3. In combination in apparatus for regulating the density of a mixture of abrasive and water in a tank, a feeding device for supplying sand to the tank, and regulating means for the feed means comprising a pair of upright tubes in the tank extending down to different levels therein and having enlargements at their upper ends extending above the surface of the mixture in the tank, a lever upon which the tubes are supported so that they tend to counterbalance each other, and an electric circuit for controlling the feed means, and a switch in said circuit actuated by the relative vertical movement of the tubes whereby the feed means is stopped and started depending upon variations in the density of the mixture at the lower ends of said tubes.

t. In combination in apparatus for regulating the density of a mixture of abrasive and water in a tank, a feedin device for supplying sand to the tank, an regulating means for the feed means comprising a pair of upright tubes in the tank extending down to different levels therein and having enlargements at their upper ends lying partially above and partially below the level of the mixture in the tank, a lever upon which the tubes are supported so that they tend to counterbalance each other, and means actuated by the tendency toward relative vertical movement by the tubes for governing the feed means,

5. In combination in apparatus for regulating the density of a mixture of abrasive and water in a tank, a feeding device for supplying sand'to the tank, and regulating means for the feed means comprising a pair of upright tubes in the tank extending down to difierent levels therein and having enlargements at their, upper ends lying partially above and partially below the level of the mixture in the tank, a lever upon which the tubes are supported so that they tend to counterbalance each other, indicator means, an electric circuit governing said indicator means and said feed means, and means actuated by the tendency toward relative vertical movement by the tubes for controlling the flow of current through said circuit.

6. In combination in apparatus for regulating the density of a mixture of abrasive and water in a tank, a feeding device for supplying sand to the tank, and regulating means for the feed means comprising a pair of upright tubes in the tank extending down to different levels therein and having enlargements at their upper ends lying partially above and partially below the level of the mixture in the tank, a lever upon which the tubes are supported so that they tend to counterbalance each other, indicator means, an electric circuit governing said indicator means and said feed means, and means actuated by the tendency toward relative vertical movement by the tubes for controlling the tlow of current through said circuit, the said indicator means comprising a pair of different colored lghts arranged so that one of them is lighted by the current in the circuit when the feed means is working and the density of themixture is below a predetermined point and so that the other is lighted by the current in the circuit when the feed means is not working and the density of the mixture is above a predetermined point.

- 7. In combination in apparatus for regulating the density of a mixture of abrasive and water in a tank, a feeding device for supplying sand to the tank, and regulating means for the feed means comprising a pair of upright tubes in the tank extending down to difierent levels therein and having enlargements at their upper ends extending above the surface of the mixture in the tank, a lever or beam upon which the tubes are supported so that they tend to counterbalance each other, shiftable balancing means for the beam, and means actuated by the relative vertical movement of the tubes for governing the feed means.

8. In combination in apparatus for regulating the density of a mixture of abrasive and water in a tank, a feeding device for supplying sand to the tank, and regulating means for the feed means comprising a pair of upright tubes in the tank extending down to different levels therein and having enlargements at their upper ends extending 'above the surface of the mixture in the tank, a lever upon which the tubes are supported so that they tend to counter-balance each other, means actuated by the relative vertical movement of the tubes for governing the tube feed means and means for supplying a flow of water downward into the upper ends of the tubes to promote thesettling out of any abrasive Whichmay be carried upward into the lower ends of the tubes.

in testimony whereof, I have hereunto ggggcribed my name this 20th day of April natenn'r K. irrrer-roook. 

